Municipal wastewater treatment and disposal facilities are recognized sources of urban methane emissions and are accounted for in Canada’s national greenhouse gas inventory. However, less is known about the emissions from the wastewater collection system that transports sewage from residences to treatment plants. One possibly considerable yet underexamined source is sewer access points (i.e., manholes), which provide a pathway for methane-rich sewer gas to escape into the atmosphere. In large cities like Calgary these access points are numerous and widespread, representing tens of thousands of potential emission sites. However, strategic mitigation policy targeting this source type cannot be implemented while its emission profile remains poorly understood.
The purpose of this ongoing research is to characterize and quantify methane emissions from sewer access points. This is being done by screening for elevated methane and directly measuring emission rates at hundreds of randomly selected sewer access points. The extensive and randomized sample size makes this project the most representative and largest known study specific to sewer access points to date. The collected measurement data will be upscaled using modelling techniques to estimate the contributions of sewer access point emissions to Calgary’s overall methane footprint.
Project lead: Joseph Samuel